1. Field of the Invention
The present invention relates to an air pressure regulator, and more particularly to a piston body, wherein a stable output and a high accuracy of the secondary pressure can be ensured without gas leakage and without changing the output pressure influenced by the primary pressure amount by means that both the resilience of the return spring connected thereto and the high-pressure gas create a coordination effect.
2. Description of the Prior Art
Conventionally, some gases, e.g. oxygen, acetylene, nitrogen, argon etc. are bottled in high pressure for the use in the industry. Before the bottled high-pressure gas is used, the gas pressure must be adjusted to an appropriate extent by means of an air pressure regulator so as to ensure a normal use and safety of the instrument piping, tools and equipment. The main function of the air pressure regulator is to stabilize the output of the secondary pressure.
FIGS. 1 through 4 show a conventional air pressure regulator. The inside of the main body 1 screwed with an upper cover 11 is divided into a primary pressure chamber P1 and a secondary pressure chamber P2. The primary pressure chamber P1 is connected with an air inlet pipe 12 and a primary pressure gauge 13 while the secondary pressure chamber P2 is connected with an air outlet pipe 14, a secondary pressure gauge 15 and safety valve 16. A valve 17 with a small spring 171 at the bottom thereof is provided between the primary and secondary pressure chamber P1, P2 to control the opening and closing of the passage. Furthermore, an accommodation 111 is formed in the middle of the upper cover 11 while a flange is disposed at the lower end thereof which is connected with an elastomer piece 18 so as to couple with the valve 17 for a synchronic motion, whereby the secondary pressure chamber P2 and the accommodation 111 are separated. Thereafter, a screw through hole is provided at the top of the upper cover 11 for installing an adjusting screw 113 elongating into the accommodation 111 fitted with a large spring 19 whose upper end is provided with a packing piece 191 pressed by the adjusting screw 113 while the lower end thereof is suppressed on a metallic packing piece 181 disposed in the middle of the elastomer piece 18.
However, the pressure of the secondary pressure chamber P2 is adjusted by means of the adjusting screw 113 in the knob 114 adjusting the position of the large spring 19 so as to create pressure suppressing the curved position of the elastomer piece 18. Furthermore, it also controls the opening and closing of the valve 17 to form a loop and commands the high-pressure gas flowing from the primary pressure chamber P1 to the secondary pressure chamber P2. When the gas pressure in the secondary pressure chamber P2 is greater than that of the large spring 19 at the top of the elastomer piece 18, as shown in FIG. 4, it will be deformed to be curve-shaped. At this time, the valve 17 will rise through the resilience of the small spring 171 at the bottom thereof to close the valve hole 172 of the primary pressure chamber P1. When the pressure in the air outlet pipe 14 is released, the pressure in the secondary pressure chamber P2 will be lowered. At this time, the elastomer piece 18 will be pushed by the resilience of the great spring 19 and deformed again and restored to be a curved shape, as shown in FIG. 3. The top rod 173 of the valve 17 is suppressed by the metallic packing piece 181 in the middle thereof to be lowered so that the valve hole 172 is open to let the gas in the primary pressure chamber P1 flow into the secondary pressure chamber P2 again. In accordance with the above-mentioned procedure, the pressure in the secondary pressure chamber P2 are unceasingly adjusted and controlled for ensuring a desired pressure output.
Therefore, the elastomer piece 18 is unceasingly deformed. As it owns the elasticity, it will age and easily loses its elastic feature after a longer using period. If it is used in the corrosive gas, it's likely to cause leakage of the poisonous gas. Besides, the elastomer piece 18 is frequently produced with an uneven thickness so that it's likely to result in deformity at the thinner position, whereby the area of thrust surface is also influenced.
Moreover, the output of the secondary pressure is adjusted by means of the flexible elastomer piece 18 controlled by the large spring 19 and the metal packing piece 181 adjustable through the adjusting screw 113 of the knob 114, so that the adjustment at an exact position can't be ensured. In addition, the high pressure in the steel cylinder will be changed with using, e.g. the pressure in the steel cylinder full bottled with high-pressure gas is 150 kg/cm.sup.2. When it runs out, it's likely that only 10 kg/cm.sup.2 of the pressure remains. Such a huge pressure difference will result in the unstable pressure output of the primary pressure chamber P1 and also easily influences the valve 17 in the primary pressure chamber P1 and the small spring 171 at the bottom thereof. The resilience of the small spring 171 controlling the rise of the valve 17 is very slight so that the influence of the pressure difference upon the valve is relatively huge and the accuracy to control the gas flow will be influenced as well. It's an inevitable disadvantage. Finally, the flexible elastomer piece 18 will be shaken upwards and downwards to be deformed due to the negative pressure and the pressure instability.